I started the engine in my '24 and went to switch it to mag but accidentally switched it to off for a second or so. The pistons were still spinning a little, and I switched it back to bat to start it again. BIG mistake. Made a really really loud POP! and quit. So I started it again and it was running for a bit and it quit on it's own after about 30 seconds. As it was running I noticed it sounded really weird so I looked it up and whattaya know, I blew my muffler open. But what I'm more worried about is that it won't start now. I read that other people have had their muffler blown open, but didn't see anything about them not running anymore. What should I do?

Yeah, those thirty seconds of run-time mean you didn't break anything ruinously expensive (like the crankshaft). If cars are anything like airplanes—and they are—you can get a big backfire from a lean mixture (scares the heck out of passengers, but if your passenger happens to be a pesky in-law, the temptation can become too great to resist). It's too simple and easy a thing not to check before you do anything else. Such leanness can be caused by the kind of problem Mike mentioned.

(For a story on what else can scare the heck out of a pesky in-law in an airplane, send me a PM).